(a) Field of the Invention
The present invention relates to a refrigerating process and apparatus utilizing a refrigerating mixture. It concerns first a refrigerating process of the type in which a gas mixture undergoes a cycle comprising steps of compression at a high pressure of the cycle, of condensation by cooling at the high pressure, of expansion at a low pressure of the cycle and of vaporization at the low pressure.
(b) Description of Prior Art
The known cycles of refrigeration which utilize a pure substance as refrigerating fluid produce changes in this fluid between two temperatures, low T1 and high T2, and between two pressures, low P1 and high P2. In order that the cycle be economical and reliable, P1 is not chosen below atmospheric pressure; on the other hand, P2 is limited in its upper value by a maximum pressure which is lower than the critical pressure PC of the pure substance. Indeed, beyond this maximum pressure, the irreversibility of the thermodynamic cycle increases considerably. On the other hand, the high temperature T2 is usually room temperature to enable the use of a water or air condenser.
To reach lower cold temperatures, the technique of the so-called known cascade type has been proposed, which utilizes a succession of refrigerating cycles each using a pure substance. This solution is efficient but costly and not very reliable, since it utilizes a large number of compression machines.
To be able to rely on a single compressor, it has been proposed to use the processes of the type indicated above, according to the technique of the so-called "incorporated cascade". This solution has been found to be complicated to use and is only justifiable for large apparatuses.